B. Air Quality
2: A Context for Environmental Health
Objective: to set a context for my environmental health core lectures. Of course, it can help prepare you for my exams, but it may also help prepare you for future work as an environmental or occupational health professional.
As you will soon discover, my favorite answer to questions asked in class is "it depends." For example, "Is this chemical a health hazard?" Well, it depends on the exposure. "Can this microbe kill you?" It depends on who it infects. "How should you protect yourself against radiation exposures?" It depends on the type of radiation (as well as many other variables!).
If you've already studied statistics, you'll recognize each of these answers as dependent variables (hence the phrase "it depends"). To put it more simply, consider the context of each problem . Amateurs may happily accept simple answers, but professionals must dig for a deeper understanding. To do this, I suggest three major models for analyzing our environmental health issues.
1. Exposure - effect - control
This first context is really just a restatement of environmental health.
First, we study environmental issues primarily through human exposures. Second, we study health issues as the major effect of concern. Third, we differ from various scientific disciplines because we prescribe controls to help solve problems.
This model will help sort out your questions in chronological order . For example, I generally start each section by discussing the movement of agents through the environment. Be patient with your questions about health effects or environmental controls! We must first understand the sources of our environmental agents before we can address their health effects or specific controls.
2. Multi-media models
According to an EPA study in Philadelphia (some years ago), where was the largest single source of their air pollution? (Hint: it's not cars, because in this study they considered each car to be a single source). Give up? Their largest single source was a wastewater treatment plant! It turns out that it produced much more than a bad smell! This is a simple example of how treating one pollution (wastewater) leads to another form of pollution (air pollution). But why stop there? All of our environment is inter-linked! Can treatment processes chase pollution in circles?
Consider the three major phases in nature: solid, liquid, and gas
water-air: this is represented by the Philadelphia study mentioned earlier. Further examples include: air-water: acid rain (rain cleans the air but can damage the rest of the environment). water-solid: wastewater sludge is the solids left over after treatment. solid-water: if we place solid waste into landfills, all too often they end up leaking into groundwater supplies. air-solid: various filters can remove particulates from air pollution, but the collected residue may be a nasty solid waste. solid-air: incinerators can dispose of solid wastes but may create air pollution.
In each case, good intentions for resolving one problem result in creation of another problem. So, what's the real problem? It is the nature of humans to be caught in vicious cycles , and the only way to break from these cycles is to see a larger picture. In this case, the larger picture is the multi-media nature of environmental problems.
This leads me to a warning. This class focuses on separate media of the environment (e.g., air and water). We must use these conceptual building blocks to introduce various terms in our profession. However, our true challenge is to go beyond that.
3. Who, what, when, where, how, why
Environmental health involves the work of a detective. We must constantly make diagnoses of environmental problems and prescribe solutions. The key questions, which we call interrogatives , are the same for any detective: who, what, when, where, how, and why.
Who? Who are the high risk groups? For example, are they the elderly, or newborns? Who can help us solve the problem? For example, do we need a lawyer? Teamwork is essential to every environmental health professional, and the development of a network of professionals is an important aspect addressed by this interrogative.
Also, the context of environmental health depends on the participants. Journalists look for the more sensational elements of a story, but they ask the same interrogatives. Attorneys, of course, take a more legalistic tone, but they too use the same interrogatives. Rock musicians, movie and television actors, and other public figures may also gain attention by asking these interrogatives, although what may be most notable are the questions that they don't ask. All play an important role in environmental issues, and risk communication helps us in addressing these different groups.
What? What's the problem? What's the solution? Risk assessment helps answer these questions, because the real root of most environmental problems is usually an underlying risk. Risk assessment also addresses questions of when and where.
When? When is this a problem? By understanding the timing of an environmental problem, we can prescribe preventive action. Life cycle analysis is especially helpful in analyzing this part of the problem. Acute problems with a short lifetime are sometimes more dramatic and easier to understand, but chronic problems dominate our societies and are more demanding for life cycle analysis.
Where? Where is this a problem? Our previous discussion that considered a multi-media perspective is a perfect example of this question. Furthermore, we can ask "what is the spatial scope of environmental evaluation?" For example, is it indoors only? If it includes outdoors, is it regional or global in scope?
How? How should we analyze this problem? Our choice among analytic methods has a huge influence on the solutions we prescribe. For example, if a citizen complains about water quality, is it a chemical question or is it a psychological question? A psychologist might analyze the fears and concerns of this citizen, while a chemist would examine water content. Which approach is right? Well, it depends. If that citizen is a paranoid schizophrenic complaining of marijuana contaminating her drinking water supply, then most would agree this is a psychological problem. (It's hard to believe, but yes, such a complaint really happened to me some years ago!). However, if remnants of a documented gasoline spill were making their way towards a known groundwater supply, then a background in chemistry is essential. (Yes, this too is another one of my true stories). The multi-disciplinary nature of environmental health constantly challenges us with which method is most appropriate. I gave you some easy examples, but we will soon see that this question is formidable.
Why? In enforcement activities, why do we require a given action? The answer is usually that it's the law! But how do we examine laws? Risk management offers us insights into this question. What is our ultimate professional purpose: do we save lives, money, or energy, or do simply save face? Environmental health professionals would most likely answer that our purpose is to save lives. An economist would answer money, and a physicist would answer energy (and make a powerful argument with the laws of thermodynamics and environmental sustainability). But politicians, long known for saving face, would usually have final word in the form of law. All of these answers play a role.
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For more information, try: Introduction
3: Risk Analysis
Objective: to provide a model for analyzing the various risks associated with environmental health.
Risk analysis is a broad term that represents a collection of approaches and disciplines devoted to all aspects of risk issues. At a minimum, risk analysis includes 1) risk assessment, 2) risk communication, and 3) risk management (all defined below).
Risk assessment is the characterization of adverse effects from exposure to hazards. Probably the simplest example of this characterization is to say "the risk of cancer from a lifetime of exposure to "chemical X" is greater than one out of a million." More formally, risk assessment includes four steps defined below: hazard identification, dose response assessent, exposure assessment, and risk characterization.
Hazard identification is to determine whether a particular agent is causally linked to particular health effects. For example, does this chemical cause cancer?
Dose-Response Assessment is to determine the relationship between the magnitude of exposure and the probability of occurrence of health effects in question. For example, one ounce of "chemical X" will kill 50% of laboratory mice.
Exposure Assessment is to determine the extent of human exposure (this is especially useful both before or after the application of regulatory controls). For example, after the Clean Air Act revisions have been put into place, the exposure to the average citizen to "chemical X" is 50% of the allowable standard.
Risk characterization is to describe the nature and often the magnitude of human risk, including attendant uncertainty. For example, "chemical X" may cause cancer deaths in anywhere from 3 to100 people in Los Angeles over the next 20 years.
Risk communication is an interactive exchange of information and opinions among individuals, groups, and institutions regarding risk.
Risk management is the evaluation, selection, and implementation of alternative risk control actions.
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For more information, try: Introduction